def test_2(self): self.assertEqual(factorial_digit_sum(2), 2)
def test_1(self): self.assertEqual(factorial_digit_sum(1), 1)
def test_10(self): self.assertEqual(factorial_digit_sum(10), 27)
def test_project_euler_input(self): self.assertEqual(factorial_digit_sum(100), 648)
def test_4(self): self.assertEqual(factorial_digit_sum(4), 6)